1. Field of the Invention
The present invention relates to a process for producing 4-benzoyl-5-hydroxypyrazoles or basic salts formed by the hydroxy group thereof (hereinafter referring to as 4-benzoylpyrazole derivatives) which are useful as active ingredients or intermediates of herbicides, or stabilizers against heat, oxidation or ultraviolet light. More particularly, it relates to a process for producing 4-benzoylpyrazole derivatives by a condensation reaction of a pyrazolone derivative, tetrachloromethane and a benzene derivative in the presence of an aluminium halide followed by a hydrolysis reaction.
2. Description of the Prior Arts
Heretofore, it has been known to produce 4-benzoylpyrazole derivatives by a reaction of a pyrazolone derivative with a benzoyl halide derivative in U.S. Pat. No. 4,063,925; and U.S. Pat. No. 4,008,200. In the processes, a 5-benzoyloxypyrazole derivative is produced as an intermediate and then, the benzoyl group at 5-position of the intermediate is rearranged at 4-position to obtain a 4-benzoylpyrazole derivative. Thus, the benzoyl halide derivatives used as the starting materials in the process have irritative properties and they are difficult to handle. Moreover, the benzoyl halide derivative has been produced by a chlorination reaction of a side chain of toluene or a halogenotoluene followed by a hydrolysis reaction of the resulting product. The benzoyl halide derivative has been also produced by oxidizing toluene or halogenotoluene and reacting the resulting benzoic acid derivative with phosphorus trichloride, phosgen or thionyl chloride. The process comprises many steps and is expensive.
Further, the present inventors have filed a patent application in the United States (U.S. patent application Ser. No. 240,313) which relates to a process for producing a 4-benzoylpyrazole derivatives by a condensation reaction of a pyrazolone derivative and a benzotrichloride derivative, followed by a hydrolysis reaction. However, the process still has certain industrial disadvantages.